Click on the picture of Ashurbanipal on the web site for the streaming
video.

Check The Five Great Monarchies of the Ancient World by Rawlinson:

". and the Diyaleh (ancient Gyudes), which is received between Baghdad
and the ruins of Ctesiphon. By the influx of these streams the Tigris
continues to grow in depth and ..."

The Works of Sir Thomas Browne:

"Cyrus, being impeded on his march to Babylon by the Gyudes, a deep and
rapid river, which falls into the Tigris ."

I notice there is some confusion with the Gyudes being the Karkeh or the
next river north, the Diyaleh. Both would come from "Cush" but the
Diyaleh joins the Tigris further upstream than I think fits the
description in Genesis. That is, if the Gyudes is the Gihon.

On my web page is an eleven minute streaming video of a talk I gave at
Eastern Mennonite University. That was the context of this portion of
the talk. Specifically, the Cushites, descended from Noah's grandson
originally took the area in Iran known today as Khuzistan from where the
Kassites came. The Gihon evolved to the "Gyudes" and was renamed the
Karkeh in more recent times.

What makes placing the descendants of Noah difficult with any finite
precision is that they didn't always stay put. Remember Abraham? We
know of his travels from Mesopotamia to the land of Canaan due to the
author of Genesis taking pains to tell us exactly where he went. But
the other lines of descent, although we know somewhat where they went
initially, traveled around due to wars and whatnot. The fierce
Assyrians frequently pounded their neighbors forcing them to relocate.
Josephus apparently was thrown off track and suggested the Nile River as
the Gihon due to later Cushite migrations who took their river with them
when they went!

Have the identities of the two lesser-known rivers in the Garden of Eden
been correlated very well with any dry river beds or canals in
Mesopotamia, or any other such geographical feature anywhere in the
Middle East?

I sometimes wonder because one of the rivers was said to snake around
the entire land of Kush. A land called Kush was well known to the
people of Moses' time and especially to people who had been living in
Egypt, which bordered and traded with this land of Kush. Furthermore,
the Nile follows a 270 degree arc that literally goes around the land of
Kush. So if there was a river in Eden said to go all around the land of
Kush, then how could the Jews at the time of the Exodus understand it to
be anything other than the Nile? Why would Moses refer to a different
land of Kush without distinguishing it from the one that was well known
just south of Egypt?

Futhermore, the river Ceyhan that goes through the land of the Hittites
sound phonetically equivalent to the river Gihon in the garden. I
sometimes wonder if these four rivers were allegorically representing
civilizations in general -- Ceyhon through the Hittites, Pishon (Nile?)
through Kush and Egypt, Tigris through Assyria and Euphrates through
Babylon.